The invention relates to the field of ophthalmology.
The cornea is a transparent epithelium layer covering the iris, pupil and anterior chamber of the eye. Incoming light is refracted by the curvature of the cornea, contributing to the eye's focusing power. The cornea is typically circular in shape, with a diameter of approximately 10 mm and thickness ranging from 50-70 μm, that rests on top of the Bowman's membrane or layer, which in turn covers the major corneal stroma. The epithelium is a layer of fast growing and easily regenerated cells that blocks the passage of foreign bodies and provides a smooth surface for distributing oxygen and nutrients from tears. Although the epithelium has no blood cells it does have nerve cell endings. An eroded, cut, damaged, dystrophied or diseased corneal epithelium can be removed to regenerate itself in about 2-3 days. However, while the epithelium is regenerative, the underlying Bowman's membrane is not.
The epithelium may also be removed as a precursor to laser refractive surgery, which is a corrective eye surgery that utilizes an excimer laser to change the curvature of the cornea in an effort to correct myopia, hyperopia and astigmatism. Lately, more complex ablation patterns have allowed for the correction of higher order aberrations. A fundamental step during the surgery is symmetric, rapid removal of the central and paracentral corneal epithelium, or skin layer of the cornea, to enable the laser to reshape the corneal stroma, where consistency in performing this procedure directly impacts on the results. Ideally, the epithelium is sufficiently removed to support the larger diameter of modern day excimer lasers while not exceeding an amount that would prolong healing time and increase the risk of infection.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the figures.